The present invention relates generally to turbine engines, and more particularly, to systems and methods for securing turbine nozzles within a turbine carrier groove.
At least some known turbine engines, such as gas turbines and steam turbines, include a carrier for axially spaced, circumferential arrays of nozzles. The carrier typically includes carrier halves which extend arcuately 180° and are secured to one another at a horizontal joint face to form a 360° array of nozzles at each axial stage position. Typically, the nozzles include an airfoil having a dovetail-shaped base that is inserted in a corresponding dovetail-shaped groove in the carrier. When the nozzles are installed in each carrier half groove, the nozzle bases are stacked one against the other within the grooves forming a semi-circular array of nozzles.
One known method of retaining the nozzles within the grooves includes using shims to secure the nozzle in the proper position. However, shims have to be accurately cut and selectively assembled to fit each nozzle. If the shims are not accurately cut, the nozzle may jam when being installed over the shims, resulting in decreased efficiency of operation. Using shims is also a time consuming and labor intensive process, which may cause an increase in manufacturing costs.
Another known method of retaining the nozzles within the grooves includes using radial loading pins to secure each nozzle. With such method, a pin is disposed between the base of the nozzle and the base of the groove to bias the nozzle radially inwardly. The pins are typically made from steel to have high strength at room temperature assembly conditions, and high strength at high temperature operating conditions. Because of the pin material and the dovetail geometry of known nozzles, high stresses exist in the nozzle dovetail hook and an upstream ligament of the outer ring which holds the nozzle.